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Publisher's URL: http://dx.doi.org/10.1103/PhysRevC.62.014616
The12C( gamma,np) and 12C( gamma,pp) reactions have been studied using the Glasgow photon tagging spectrometer at the Mainz MAMI electron microtron for E gamma = 150-700 MeV over a kinematic range which extends well beyond the approximately back-to-back detector arrangements of previous work. For 12C(gamma,np) the general trends of the missing energy distributions are reproduced over a wide range of kinematics and photon energies by the theory developed by the Valencia group. The corresponding 12C(gamma,PP) channel is overestimated by a factor of similar to 3. Detailed comparisons of the experimental data with a Monte Carlo simulation of the direct 2N knockout process provide the first evidence above the Delta resonance for direct 2N knockout and show that this process dominates the 12C(gamma,np) reaction at low missing energies up to E gamma similar to 700 MeV. The 12C(gamma,pp) reaction is somewhat less well described by the Monte Carlo simulation. A possible explanation of the observed discrepancies within a direct 2N framework is presented. At high recoil momenta both 2N reaction channels exhibit an excess yield compared to the Monte Carlo prediction of direct 2N knockout. The excess yield in this region is compared with the predicted effects of short-range correlations and with the predicted contributions due to other reaction mechanisms.
|Glasgow Author(s):||Branford, Prof Derek and Watts, Dr Daniel and McGeorge, Dr John and Owens, Prof Robert and MacGregor, Dr I and Annand, Dr John and Kellie, Dr James|
|Authors:||Watts, D.P., MacGregor, I.J.D., Ahrens, J., Annand, J.R.M., Beck, R., Branford, D., Grabmayr, P., Hall, S.J., Harty, P.D., Hehl, T., Kellie, J.D., Lamparter, T., Liang, M., MacKenzie, J.A., McAllister, S.J., McGeorge, J.C., Owens, R.O., Sauer, M., Schneider, R., Wagner, G.J., and Yau, T.T.H.|
|Subjects:||Q Science > QC Physics|
|College/School:||College of Science and Engineering > School of Physics and Astronomy|
|Journal Name:||Physical Review C|